U.S. Pat. No. 3,767,756 describes a process for spinning para-aramids to provide fibers having excellent as-spun tenacity, modulus and breaking elongation. The p-aramid fibers obtained by the above-referenced spinning process have excellent properties but even further improvement in tenacity and modulus is often desired. U.S. Pat. No. 3,869,429 teaches that drying para-aramid fibers obtained using such processes under tensions less than about 0.3 gpd is preferred; but, that drying the fibers above 0.3 gpd reduces the breaking elongation of the fibers while increasing the modulus.
Japanese Laid-Open Patent Application (Kokai) Ser. No. 98,415/78 discloses a post spinning drying treatment of para-aramid fibers wherein the fibers are subjected to a single-step drying under a constant draw-ratio of about 20-90% of ultimate fiber elongation at a temperature of less than about 200.degree. C.
Japanese Patent Publication No. 11763/80 discloses a post-spinning fiber treatment of para-aramid fibers wherein the fibers: are drawn about 20-80% of maximum elongation at a temperature of less than 100.degree. C. while retaining residual spinning solvent in an amount of 100% of the weight of the dry fiber; are washed to remove the residual spinning solvent; and are dried and heat treated at a temperature greater than 300.degree. C. under tension which would provide constant length.
Japanese Patent Publication No. 11764/80 discloses a post-spinning fiber treatment of para-aramid fibers wherein the fibers: are washed in water; are drawn about 20-90% of maximum elongation while wet and in saturated steam at a temperature of greater than 100.degree. C., and are dried and heat treated at a temperature greater than 300.degree. C. under tension which would provide constant length.
Japanese Laid-Open patent application (Kokai) Ser. No. 88,117/85 discloses a post-spinning drying treatment of para-aramid fibers wherein the fibers, with greater than 50% water, are subjected to a stretching step through application of tension of 1-10 gpd and are then subjected to a drying step wherein the same length as with the tension applied is maintained all at a temperature of less than 200.degree. C.
Japanese Laid-Open patent application (Kokai) Ser. No. 167,015/86 discloses a post-spinning drying treatment of para-aramid fibers wherein the fibers are subjected to a tensionless preliminary dewatering to reduce the water content to about 20-80% and are then subjected to a single-step drying under a constant tension of 5-15 gpd and at a temperature of 50.degree.-150.degree. C.